Hello,

I have a 2005 MINI Cooper S, and it has been in the shop for 2 weeks now. The dealer told me it is an air leak in the cylinder head. Apparently, when they made the cylinder head from the mold, the metal didn't completely set. I was wondering if any of the other 2005 owners have the same problem? It appeared 1 month after owning the car, and the EML light as well as the service engine soon light appeared. Please help.

 

If the defect was on the lower head surface, the car would have blown a head gasket almost immediately. If we are to believe the "air leak" diagnosis, it is a defect in the upper part of the head where it meets the valve body that meters air into the cylinders. This is not as serious as the head gasket being blown, but it will cause a change in the air/fuel ratio that set off the EML light. Chances are it is a small leak, or it would have turned up sooner. A defective head sounds awful, but it really may be minor problem. Quality control was probably off for Boxing Day or Guy Falkes Day.

 

Well, the engine is made in Brazil, so probably quality control was out at the Rio Carnaval or taking Samba lessons that day...

 

This is actually a rather common problem with anything made from cast aluminum. Heads, blocks, transmissions, anything made of a cast material can be affected by 'casting porosity', where the metal does not flow tightly in the mold, or suffer from casting sand 'inclusions' and impurities in the metal. Yours must have been quite severe to cause such a problem so soon. It's a simple fix once it's found, just replace the offending part. If they have none in stock, tell them you'll settle for a JCW head in it's place.

I havent heard too much in the way of 'inherent' head troubles with MINIs yet, but I dont expect them to remain problem-free on the long run. Any engine such as out beloved little 1.6 which has an iron block capped with an aluminum head suffers from a difference in thermal expansion between the two materials. Aluminum 'moves' more than iron when heated and cooled repeatedly, and over time the head gasket, even though it's designed to allow this movement between the two elements will eventually fail. So far, with people going for some rather big horseppower from out tiny engine, there have been very few blowups. For a little motor, it's very strongly built.

 

So they found the real problem. It was a plastic tube coming from the supercharger that had a tiny hole in it. They said this was causing the small leaks in the cylinder head and the gasket.

 

The "hole in the intake tube" issue seems to be common. We had the same thing fixed about 2 weeks ago.

-Dave & Stacy